A complete accelerometer typically includes three micro-electromechanical (MEM) dies each mounted in a ceramic leadless chip carrier package forming a sensor chip mounted on a printed circuit board. Application specific integrated circuit (ASIC) chips, one for controlling each sensor die, are also mounted on the printed circuit board as are digital gate array chips and decoupling capacitor chips. Typically, there are numerous electrical interconnections between each sensor chip and each ASIC chip and many (a hundred or more) electrical interconnections between each ASIC chip and each digital gate array chip.
Those skilled in the art understand that the sensor chip packages must be mounted in close proximity to the respective ASIC chips and that the digital gate array chips must be mounted in close proximity to their respective ASIC chips to minimize the length of the electrical interconnections therebetween and thereby reduce parasitic capacitance and noise susceptibility.
Thus, it is conventional to place the ceramic leadless sensor chip carrier packages on one side of a printed circuit board and mount the ASIC chips via ball grid arrays on the other side of the printed circuit board opposite each ceramic leadless sensor chip carrier package. The digital gate array chips are also mounted to one side of the printed circuit board as are the decoupling capacitor chips. Wire bonds, the printed circuit board circuitry, and vias through the printed circuit board structure provide the required electrical interconnections.
As the sensors are made more sensitive, however, parasitic capacitance and noise are still problems.